The present invention relates to a method of manufacturing a molded piece of plastic that is painted, and to pieces obtained by implementing the method.
In order to paint a piece of plastic in part, a masking technique is used, consisting in depositing a mask on a zone of the piece, in painting the piece provided with the mask in full, and in removing the mask after painting in order to uncover the non-painted portion of the piece.
The mask used for that purpose is generally a self-adhesive tape that is placed on the piece immediately before the painting operation.
Such placing of the mask involves a considerable amount of labor, and corresponds to a non-negligible portion of the time required to make the piece.
In addition, the border between the painted portion and the non-painted portion, which appears after the mask has been removed, generally has portions that are uneven and portions that have excess thickness. In addition to spoiling the appearance of the piece, such portions also weaken the paint by making it easier for it to come unstuck.
In addition, when a piece is to be painted in a plurality of colors, it is necessary to perform a plurality of successive masking, painting, and baking operations, which gives rise to extra cost in terms of labor and of energy.
An object of the present invention is to solve those drawbacks.
The present invention provides a method of making a piece of plastic that is painted, said method being consisting in depositing a xe2x80x9cpeel-offxe2x80x9d film inside a mold defining the shape of the piece, which film is suitable for being separated easily from the support to which it is fixed, in making the piece by molding over the film, in painting the piece in full, and in removing the film so as to uncover the non-painted portion of the piece.
In the invention the xe2x80x9cnon-painted portion of the piecexe2x80x9d, is a portion that has not received any application of paint by conventional painting means, and said portion may therefore be colored by other means.
The method of the invention makes it possible to omit the step consisting in putting a mask into place on the piece before the painting operation, since, in the invention, this is achieved by depositing the peel-off film in the mold at the place corresponding to the non-painted portion of the piece.
In a first implementation of the invention, the peel-off film is fixed temporarily by adhesion to a sheet situated on that side of the peel-off film which faces the plastic. The sheet is overmolded during the molding of the piece, and remains bonded thereto, whereas the peel-off film can be separated from the sheet after the overmolding, and after the piece has been painted, thereby causing the non-painted sheet to appear.
In this implementation, the sheet is advantageously constituted by a colored film, so that removing the peel-off film uncovers the colored film constituting the sheet.
In this way, it is possible to make a piece having two tints: that of the paint, and that of the colored film constituting the sheet.
In another implementation of the invention, the peel-off film is made of a material that is not compatible with the plastic of which the piece is made, i.e. it adheres poorly to said plastic.
In which case, the film can be separated directly from the molded piece after said molded piece has been painted, then allowing the plastic constituting the piece to appear.
To implement the invention, the following plastics may be used for the film and for the piece: ABS (acrylonitrile-butadiene-styrene) terpolymer, TPO (thermoplastic olefin), PET (polyethylene terephthalate), PE (polyethylene), PC (polycarbonate), PMMA (polymethyl methacrylate), ASA (acrylonitrile-styrene-acrylonitrile), a PBT/PC (polybutylene/polycarbonate) alloy, a PA/PC (polyamide/polycarbonate) alloy, PVC (polyvinyl chloride), POM (polyoxymethylene), acrylic, PU (polyurethane), PTFE (polytetrafluoroethylene), and PA (polyamide).
Advantageously, the film (together with the sheet if a sheet is provided) is preformed before it is put in place in the mold, and it is cut to the exact dimensions of that portion of the piece which is to be masked.
The method of the invention is particularly advantageous for making a piece having two tints, because one of the tints can be that of the sheet temporarily supporting the peel-off film or be mixed with the plastic of which the piece is made, if the peel-off film is not fixed to a sheet, the other tint being applied by painting.
The present invention also provides pieces obtained by implementing the above-defined method, and in particular pieces having two tints.